Method of creating NC data for turning

ABSTRACT

A method of creating NC data including storing various approach/withdrawal patterns in dependence upon a particular zone in which a turret index point/tool exchange position (P T ) is present, the zone being one among zones (ZN 1  -ZN 3 ) defined by horizonal and vertical axes passing through a point (Q) specified by a safe position coordinate (Z S ) in a longitudinal direction of a workpiece (WK) and a safe position coordinate (X S ) in a direction perpendicular to the longitudinal direction, and in dependence upon a plane to which a cutting starting/end point (P S ) belongs, the plane being one of a plane (LPS) in the longitudinal direction of the workpiece and a plane (TPS) perpendicular to the longitudinal direction belongs. A predetermined pattern is selected from among the stored approach/withdrawal patterns based on the zone to which the turret index point (P T ) actually belongs and the plane to which the cutting starting/end point (P S ) actually belongs. NC data for approach and NC data for withdrawal are created using the selected pattern.

DESCRIPTION

1. Technical Field

This invention relates to a method of creating NC data for turning and,more particularly, to an NC data creation method well, suited forcreating approach and withdrawal NC data for turning.

2. Background Art

In turning performed by a lathe, as shown in FIG. 10, a desired tool TLis selected at an index position (turret index point) P_(T) of a turretTR. The tool is then made to approach a cutting starting point P_(A)(see the path indicated by the black arrows). The tool is subsequentlymoved along a commanded path at the completion of the approach operationso as to machine a workpiece WK. The tool is then withdrawn from acutting end point (which coincides with the cutting starting point)P_(A) to the turret index position P_(T) at the completion of machiningperformed by the tool (see the white arrows), thereby ending the turningcycle for one process. Thereafter, the tool for the next process isselected and the same operations are repeated, whereby a desired partprofile PFG (see the dashed line) is eventually obtained. In FIG. 10,CHK denotes a chuck. The cutting starting/end point P_(A) is a pointlocated at a distance Δd from a starting point P_(S) on the part profilePFG.

With regard to the approach path among the tool paths traversed in sucha turning operation, there is a case (i) where a direct approach is madeby rapid-traverse positioning using the machining starting point (turretindex point) P_(T) and the cutting starting point P_(A) as therespective starting and end points (see a first approach path PTA₁), anda case (ii) where a suitable transit point (e.g., a point P_(AA) orP_(AS)) is entered and this point is traversed (see second and thirdpaths PTA₂, PTA₃). The same is true for the withdrawal path. It shouldbe noted that the cutting path is automatically decided by entering thepart profile.

When the direct approach or withdrawal of case (i) is made, the approachand withdrawal distances can be shortened but a problem which arises isthat the tool may be obstructed by obstacles such as a stationaryportion of the machine, the workpiece, etc.

When approach or withdrawal is made so as to traverse the designatedtransit point as in case (ii), it can be arranged so that the tool willnot interfere with the workpiece, but the transit point for the approachor withdrawal must be designated each time the approach or withdrawal isperformed. This is a troublesome operation.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide a methodof creating NC data for turning, wherein an approach path and withdrawalpath which will not cause interference with an obstacle can be decidedwithout entering a transit point.

In a method of creating NC data for turning according to the presentinvention, various approach/withdrawal patterns are registered independence upon a particular zone in which a turret index point ispresent, the zone being one among zones defined by horizontal andvertical axes passing through a point specified by a safe positioncoordinate in a longitudinal direction of a workpiece and a safeposition coordinate in a direction perpendicular to the longitudinaldirection, and in dependence upon a plane to which the cuttingstarting/end point belongs, the plane being one of a plane in thelongitudinal direction of the workpiece and a plane perpendicular to thelongitudinal direction. A predetermined pattern is selected from amongthe registered approach/withdrawal patterns based on the zone to whichthe turret index point actually belongs and the plane to which thecutting starting/end point actually belongs. NC data for approach and NCdata for withdrawal are created using the selected pattern.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view for describing the principle of the NC data creationmethod of the present invention;

FIG. 2 is a block diagram of a system for executing the method of theinvention;

FIGS. 3(a) through 8(c) are views of approach/withdrawal patterns;

FIG. 9 is a flowchart of processing according to the invention; and

FIG. 10 is a view for describing paths used in a lathe.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 is a view for describing the principle of the NC data creationmethod of the present invention. WK represents a workpiece, PFG (thedashed line) a part profile, Z_(S) a safe position coordinate in thelongitudinal direction of the workpiece, X_(S) a safe positioncoordinate in a direction perpendicular to the longitudinal direction ofthe workpiece, X_(A) a cutting starting/end point, P_(T) a turret indexposition, ZN₀ -ZN₃ zones, LPS a plane (longitudinal plane) parallel tothe longitudinal direction of the workpiece, and TPS a plane parallel tothe end face of the workpiece.

Various approach/withdrawal patterns are registered in dependence upon aparticular zone in which the turret index point P_(T) is present. Thezone is one of the zones ZN₁ -ZN₃ defined by horizontal and verticalaxes passing through a point Q (Z_(S),X_(S)) specified by the safeposition coordinate Z_(S) in the longitudinal direction of the workpieceand the safe position coordinate X_(S) in the direction perpendicular tothe longitudinal direction. The zone is selected in dependence upon aplane to which the cutting starting end/point P_(A) belongs, the planebeing one of the plane (longitudinal plane) LPS in the longitudinaldirection of the workpiece and the plane (end face) TPS perpendicular tothe longitudinal direction. A predetermined pattern is selected fromamong the registered approach/withdrawal patterns based on a combinationof the zone ZN₂ to which the turret index point P_(T) actually belongsand the plane LPS to which the cutting starting/end point P_(A) actuallybelongs. NC data for approach and NC data for withdrawal are createdusing the selected pattern.

FIG. 2 is a block diagram of an automatic programming system forpracticing the method of creating NC data for turning according to thepresent invention. Numeral 11 denotes the main body of the system, whichincludes a processor (CPU) 11a, a program memory (ROM) 11b for storing aloading program and the like, and a RAM 11c which stores a systemprogram for NC data creation read in from a floppy FL, approach andwithdrawal patterns, as well as the results of processing, etc.

Numeral 12 denotes a keyboard, 13 a graphic display unit, 14 a diskcontroller, and 15 an NC data output unit for outputting created NC datato an external storage medium (NC tape). The floppy FL stores the systemprogram for creating NC data, the approach/withdrawal patterns, etc.

FIGS. 3(a) through 8(c), which are views for describing theapproach/withdrawal patterns, show six respective cases in conformancewith the turret index P_(T) and cutting starting/end point P_(A) ; threetypes of patterns are set for each case. More specifically, threeapproach/withdrawal patterns are set and registered on the floppy FL, asshown in FIGS. 3(a) through 8(c). These patterns represent respectiveones of six cases for combinations of the area in which the turret indexposition P_(T) resides. The area is one of the areas ZN₁ -ZN₃ defined byhorizontal and vertical axes passing through the point Q specified bythe safe position coordinate Z_(S) in the longitudinal direction of theworkpiece and the safe position coordinate X_(S) in the directionperpendicular to the longitudinal direction, and the plane (longitudinalplane) LPS in the longitudinal direction of the workpiece or the plane(end face) TPS perpendicular to the longitudinal direction to which thecutting starting/end point P_(A) belongs.

FIGS. 3(a)-3(c) are for a case where the turret index point P_(T)belongs to the first zone ZN₁ and the cutting starting/end point P_(A)belongs to the longitudinal plane LPS. FIG. 3(a) shows a pattern which,in an approach operation, is for moving the tool horizontally, i.e., inthe -Z direction, at rapid-traverse from the turret index point P_(T) toa point just above the cutting starting/end point P_(A). The tool issubsequently lowered to the cutting starting/end point P_(A). In awithdrawal operation, FIG. 3(a) is for withdrawing the tool in thedirection opposite that of the approach. FIG. 3(b) shows a patternwhich, in an approach operation, is for moving the tool atrapid-traverse simultaneously along two axes from the turret index pointP_(T) to a boundary point P_(D), of a danger zone ZN₀, just above thecutting starting/end point P_(A). The tool is subsequently lowered tothe cutting starting/end point P_(A). In withdrawal operation, FIG. 3(b)is for withdrawing the tool in the direction opposite that of theapproach. FIG. 3(c) shows a pattern which, in an approach operation, isfor lowering the tool at rapid-traverse from the turret index pointP_(T) to a boundary point P_(D) ' of the danger zone ZN₀, then movingthe tool at rapid-traverse to a boundary point P_(D) along the boundaryline. The tool is subsequently lowered to the cutting starting/end pointP_(A). In a withdrawal operation, FIG. 3(c) is for withdrawing the toolin the direction opposite that of the approach.

FIGS. 4(a)-4(c) are a case where the turret index point P_(T) belongs tothe second zone ZN₂ and the cutting starting/end point P_(A) belongs tothe longitudinal plane LPS. FIGS. 5(a)-5(c) are for a case where theturret index point P_(T) belongs to the third zone ZN₃ and the cuttingstarting/end point P_(A) belongs to the longitudinal plane LPS. FIGS.6(a)-6(c) are for a case where the turret index point P_(T) belongs tothe first zone ZN₁ and the cutting starting/end point P_(A), belongs tothe end face plane TPS. FIGS. 7(a)-7(c) are for a case where the currentindex point P_(T) belongs to the second zone ZN₂ and the cuttingstarting/end point P_(A) belongs to the end face plane TPS. FIGS.8(a)-8(c) are for a case where the turret index point P_(T) belongs tothe third zone ZN₃ and the cutting starting/end point P_(A) belongs tothe end face plane TPS. Three approach/withdrawal patterns are set forthe FIGS. 4(a) through 8(c), just as in the case of FIGS. 3(a)-3(c) andthese patterns are registered on the floppy FL.

FIG. 9 is a flowchart of processing according to the present invention.The method of creating NC data according to the present invention willnow be described in accordance with this flowchart. It is assumed thatthe system program, the approach/withdrawal data and other data havealready been transferred to and stored in the RAM 11c from the floppy FLunder the control of the loading program stored in the ROM 11b.

In response to start of operation for creating NC data for turning, thegraphic display unit 13 displays a prompting screen calling for the safeposition coordinates in the Z direction (longitudinal direction of theworkpiece) and X direction. Accordingly, the safe position coordinatesZ_(S), X_(S) (see FIG. 1) along the respective axes are entered from thekeyboard 12 or the like (step 101).

The safe position coordinates Z_(S), X_(S) mean that, in a case wherethe cutting starting/end point P_(A) resides on the longitudinal planeLPS, the tool will not interfere with an obstacle even if the tool ismoved vertically toward the cutting starting/end point P_(A), or even ifthe tool is moved vertically away from the cutting starting/end pointP_(A), in the danger zone ZN₀ specified by Z_(S), X_(S). Further, in acase where the cutting starting/end point P_(A) resides on the end faceplane TPS, the tool will not interfere with an obstacle even if the toolis moved horizontally toward the cutting starting/end point P_(A), oreven if the tool is moved vertically away from the cutting starting/endpoint P_(A), in the danger zone ZN₀.

At the completion of entry of the safe position, a prompt appearscalling for the turret index position P_(T) (step 103). Therefore, thecoordinates (Z_(T),X_(T)) of the point are entered in the same manner(step 103).

Next, the part profile PFG, turning conditions and data indicative ofthe tool used are entered in the same manner as practiced in the priorart (step 105).

When the entry of the part profile and the like is completed, theprocessor considers the safe position coordinates Z_(S), X_(S) along therespective axes and the coordinates Z_(T), X_(T) of the turret indexposition P_(T) to determine the zone to which the turret index positionP_(T) belongs (step 107), and determines, from the starting point P_(S)of the part profile PFG, the plane to which the cutting starting/endpoint P_(A) belongs (step 109). If the starting point P_(S) of the partprofile PFG resides on the longitudinal surface of the workpiece WK, thecutting starting/end point P_(A) will lie at a position located adistance .sub.Δ d (already known) directly above the starting pointP_(S) and therefore will belong to the longitudinal plane LPS. If thestarting point P_(S) resides on the end face of the workpiece WK, thecutting starting/end point P_(A) will lie at a position located adistance .sub.Δ d' (not shown) from the starting point P_(S) in thehorizontal direction and therefore will belong to the end face planeTPS.

Thereafter, the processor 11a causes the first, second and thirdapproach/withdrawal patterns [e.g., FIGS. 3(a)-(c)] to be displayed inconformity with the combination of the area to which the turret indexpoint P_(T) belongs and the plane to which the cutting starting/endpoint P_(A) belongs, as determined at steps 107, 109. Along whichpattern the approach and withdrawal are to be made is entered (step111). It should be noted that it is not essential to display thepatterns.

Using the approach/withdrawal pattern entered at step 111, thecoordinates (Z_(T),X_(T)) of the turret index point P_(T), thecoordinates Z_(S), X_(S) of the safe position and the coordinates of thecutting starting/end point P_(A), the processor 11a automaticallycreates NC data for the approach (step 113), creates NC data for thecutting path using the part profile data, machining conditions, etc.,after creation of the NC data for approach (step 115), and finallycreates NC data for the withdrawal in the direction opposite that of theapproach, after which processing is ended (step 117).

The foregoing description is rendered upon taking into consideration theplane to which the cutting starting/end point P_(A) belongs, which pointis located at the position a predetermined distance from the startingpoint P_(S) of the part profile. However, it is permissible to adopt anarrangement in which the approach/withdrawal pattern is decided in asimilar manner upon taking into consideration the plane to which thestarting point P_(S) belongs.

Further, the foregoing description pertains to an arrangement in whichthree approach/withdrawal patterns exist for each of six casesconforming to the turret index position and the cutting starting/endpoint. However, the invention is not limited to this arrangement, for itwill suffice if only one pattern is provided for each case.

In accordance with the present invention, various approach andwithdrawal patterns are registered in dependence upon a combination of aparticular zone in which a turret index point is present, the zone beingone among zones defined by horizontal and vertical axes passing througha predetermined point, and the longitudinal plane or end face plane towhich the cutting starting/end point belongs. NC data for approach andNC data for withdrawal are created using a predetermined pattern fromamong the registered approach/withdrawal patterns based on the zone towhich the turret index point actually belongs and the plane to which thecutting starting/end point actually belongs. As a result, it is possibleto simply decide an approach path and withdrawal path which will notcause interference with an obstacle without deciding and enteringtransit points one at a time for the purpose of avoiding interferencewith the obstacle, as is required in the prior art.

We claim:
 1. A method of creating NC data for a tool mounted in anautomatic programming system, comprising:storing safe positioncoordinates along two orthogonal axes; storing a tool exchange position;storing a cutting starting/end point; storing a plurality ofapproach/withdrawal patterns, said patterns being based on said toolexchange position, said safe position coordinates and said cuttingstarting/end point; selecting a predetermined pattern from among saidpatterns based on said tool exchange position and said cuttingstarting/end point; and creating NC data for approach and NC data forwithdrawal using said selected pattern.
 2. A method of creating NC datafor turning according to claim 1, further comprising the stepsof:entering part profile data; and determining a plane to which saidcutting starting/end point belongs based on said part profile data.
 3. Amethod of creating NC data for turning according to claim 1, furthercomprising the steps of:storing two or more approach/withdrawal patternssaid tool exchange position and said cutting starting/end point; andselecting one of said approach/withdrawal patterns based on said toolexchange position, said cutting starting/end point and said enteredpattern selection data.
 4. A method of creating NC data for turningaccording to claim 3, further comprising the step of:displaying two ormore of said approach/withdrawal patterns based on said tool exchangeposition and said cutting starting/end point.
 5. A method of creating NCdata for turning according to claim 1, further comprises the substepof:storing said plurality of approach/withdrawal patterns including dataspecifying an approach to or withdrawal from said cutting starting/endpoint in vertical direction, and data specifying an approach to orwithdrawal from said cutting starting/end point in a horizontaldirection.